Section 136 (Anti-Lock Brake System): Description

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The Kelsey-Hayes 4-Wheel Anti-Lock (4WAL) brake system is used to prevent wheel lock-up during heavy braking. This allows driver to maintain steering control while stopping vehicle in shortest distance possible. The system consists of Brake Pressure Modulator Valve (BPMV), Vehicle Speed Sensor (VSS), VSS buffer, wheel sensors, warning lights, electrical wiring and hydraulic lines.

The BPMV consists of an Electronic Control Unit (ECU), hydraulic control unit, 2 accumulators, pump motor, and relay. See Fig 1. The hydraulic control unit consists of an isolation solenoid valve, Pulse-Width Modulated (PWM) valve, a High Pressure Accumulator (HPA), Low Pressure Accumulator (LPA) and a reset switch on each channel. If overhaul or repair to any component on the BPMV is necessary, replace complete assembly.

Fig 1: 4WAL Brake System Component Location

Courtesy of GENERAL MOTORS CORP.